1. Field of the Invention
The invention generally relates to a circuit card assembly testing system for testing and troubleshooting new and failed circuit card assemblies. Specifically, circuit card assemblies that are part of a Guided Missile and Launcher Test Set (GML/TS) are tested using a board testing system (BTS), the preferred embodiment, to isolate faults or to verify final assembly. The BTS is used for testing and troubleshooting a wide variety of circuit card assemblies at the end of final assembly, and upon their return as a failed item from the field. The BTS is designed to rapidly isolate faults in the failed circuit card assemblies that have been returned to a maintenance facility by providing an improved means of fault isolation through the use of an operational test. The BTS is designed to aid in the production of circuit card assemblies by providing an improved means of rapidly verifying the proper operation of circuit boards after final assembly by performing an operational test.
2. Description of the Prior Art
Historically, High Speed Anti-Radiation Missiles (HARM) and a Guided Missile Launcher and Test Set (GM/LTS), are designed to maintain them, are complex systems. The United States Air Force (USAF) has developed and fielded a HARM, a HARM launcher and a compatible GML/TS for use as an All Up Round (AUR) missile tester. The fielded GM/LTS was developed with the intention that the circuit board assemblies internal to the fielded GM/LTS would not be repaired. The fielded GM/LTS is equipped with an internal module self-test that identifies failed circuit card assemblies (CCAs) that cause the fielded GM/LTS to malfunction. The maintenance concept for the CCAs internal to the fielded GM/LTS is to identify and replace the failed CCA with a new CCA and then to dispose of the failed CCA. However, over time this maintenance concept has proven to be too expensive to be continued.
The USAF has decided to send the GM/LTS CCAs identified as faulted to the HARM depot for repair. Since the depot has no other means for testing the faulted GM/LTS CCAs, the depot uses a fully functioning fielded GM/LTS to perform fault isolation on the returned CCAs. Although the fielded GM/LTS is useful for identifying faulted CCAs, it is ill suited for use as a component level CCA test bed. The fielded GM/LTS accepts the faulted CCAs on a mounted closed back-plane rack that does not provide access for probing the CCA signals and is not suitable for selectively controlling the operation of the software loaded into the memory of CCA. To overcome these deficiencies and to facilitate monitoring signals during testing, wires must be manually attached to key test points in order to provide access to low level test equipment. Also, since the software operation of the CCA cannot be controlled, testing must be synchronized using an internal trigger in order to capture the failing signal events when they occur. This makes capturing and diagnosing failing signals difficult and time consuming. Also, it is often necessary to produce special versions of test software to diagnose certain problems. On average, the depot requires three months to diagnose and repair a single faulted GM/LTS CCA. Some of the CCAs require up to six months for repair.
The preferred embodiment of the board testing system (BTS) adds a new capability that reduces the time to isolate the faults present in a failed CCA, improves the accuracy in identifying faults, and provides a uniform process of repairing the faulted GM/LTS CCAs. These new capabilities that are present in the preferred embodiment allow a tester access to previously hard to access signals and also eliminates the necessity of writing and compiling tailored versions of test software.
The preferred embodiment that is the BTS is currently the only system in existence that is capable of testing and diagnosing the faulted GM/LTS CCAs. The BTS executes all internal self-tests that are preformed on the CCAs with the added feature that the BTS replicates the fielded GM/LTS and produces the exact same fail codes along with the added capability of statically pausing software execution at any point. The BTS is designed to facilitate the user's ability to diagnose problems by allowing the user to directly probe the CCAs when in a failed state. The BTS is an innovative design that combines commercial off the shelf modules with custom signal conditioning that results in a system that is both robust in test capability and is cost effective to support and maintain.